HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>id — dynamic JS</title>
  <style>
    body {
      font-family: system-ui, sans-serif;
      margin: 0;
      padding: 1.5rem;
      background: #f8fafc;
      color: #334155;
      line-height: 1.7;
    }
    h1 { margin: 0 0 1rem; font-size: 1.25rem; color: #0f172a; }
    #dynamic-element, #new-dynamic-id {
      max-width: 420px;
      padding: 0.85rem 1rem;
      background: #fff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      font-size: 0.875rem;
    }
    #new-dynamic-id { border-left: 4px solid #8b5cf6; }
    button {
      display: block;
      margin-top: 0.75rem;
      font: inherit;
      padding: 0.45rem 0.85rem;
      border: 1px solid #cbd5e1;
      border-radius: 6px;
      background: #2563eb;
      color: #fff;
      cursor: pointer;
    }
    .status {
      margin-top: 0.75rem;
      font-size: 0.8125rem;
      color: #64748b;
      max-width: 420px;
    }
    code { background: #e2e8f0; padding: 0.1rem 0.35rem; border-radius: 4px; }
  </style>
</head>
<body>
  <h1>id — dynamic JS</h1>
  <div id="dynamic-element">Current id: <code>dynamic-element</code></div>
  <button type="button" id="changeIdBtn">Change id to new-dynamic-id</button>
  <p class="status" id="status">Click the button to update the element id.</p>

  <script>
    document.getElementById("changeIdBtn").addEventListener("click", function () {
      var el = document.getElementById("dynamic-element");
      el.id = "new-dynamic-id";
      el.innerHTML = "Updated id: <code>new-dynamic-id</code>";
      document.getElementById("status").textContent = "getElementById now uses the new id value.";
    });
  </script>
</body>
</html>

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HTML id Attribute — Dynamic id with JavaScript